Scientific Name: family Ephemeroptera

Mayflies live underwater as nymphs until they reach maturity, then they hatch into winged adults called duns. The duns molt once more into a spinner that mates, then dies. Before dying, the females lay eggs in the river. A mayfly's adult life is brief, usually only a day or two.

Mayflies are sometimes divided into four major groups based on the behavior of the nymphs:

  1. Crawlers, who spend their underwater life crawling between rocks and pebbles.
  2. Clingers, who are flat little things that live in fast water and rarely lose their grip on the bottom.
  3. Swimmers, who flip their tails and swim.
  4. Burrowers, who dwell in sediment.

For details on individual species and hatches, use the pull-down menus below. You can look up a species by either its common names (each species may have more than one common name) or scientific name.

ADULT CHARACTERISTICS: Two or three tails; most have two pairs of wings, with the hind set much smaller; wings upright when at rest, except spinners' wings may be splayed to side when dying.